NOVEMBER 13, 2001More Fun with 3D in PhotoshopA second look at creating your own filtersby David Nagel

Last time around, we examined ways to use Photoshop's Filter Factory to create a 3D effect. Really I thought nobody would read it, given the limited audience for 3D graphics, but it went over surprisingly well. So this time around, I thought we'd take a look at an alternate method for generating a 3D effect and get a little deeper into the Filter Factory in preparation for our upcoming three-part series on the Filter Factory. This one, once again, will show you how to create your own filter for achieving this 3D effect.

Now, before we move on, I must caution once again that this is not a tutorial on creating the kind of 3D seen in Monsters Inc. or Final Fantasy. This is the kind of 3D that you have to wear googly red and blue glasses to appreciate--you know, the kind that makes it look like one portion of the image is closer than another. If you are interested in achieving this effect, I strongly suggest you read the previous installment. You can find it here.

Otherwise, read on....
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Last time, we broke apart portions of our image into its constituent parts and used the Filter Factory to shift the red channels of each layer a different amount. To refresh your memory, the 3D effect is achieved by shifting the red channel of an image to the left. The farther the shift, the farther away the image looks. By separating elements of an image onto separate layers, you can adjust each object's "distance" by varying the red shift on each layer.

What's the theory?
This time around, we're going to do it differently. We're going to use the background layer of an image and shift the red channel proportionally--sort of squish a portion of the image based upon the position of that portion of the image. Get it? No? Well, here's the theory.

If you shift the red channel of an image, it will look flat unless you have something to compare it with, right? 3D imagery is all about the differences in the amount of red channel shift, not the shift itself. This is the reason it worked in our previous experiment: Each layer had a unique shift in its red channel so that, compared with the other layers, it looked nearer or farther. But here we're just going to be affecting the red channel on a single layer, so we need to vary the red shift on our single layer.

Probably the most useful application for this would be a panoramic perspective shot of a wall or maybe a flying logo that trails off to the horizon. Why? What we're going to do is use Photoshop's Filter Factory and a special, magical formula to create more or less red channel shift based upon the current position of each individual pixel in our image. Sound complicated? It's not.

To begin with, choose an image that has some sort of perspective to it. For this particular technique, and image like the one below will work best. (Feel free to use this image for this experiment.) Any image will work though. If you don't have a perspective image, an image like a face can be used, with the result being that the face seems to move as the viewer's head moves. (I'll show you an example of this on the last page. It will freak you out.)